Catalytic treatment of hydrocarbon oils



Patented June 3, 1947 CATALYTIC TREATMENT F HYDRoy CARBON ons Charles Hemmnger, Westeld, and Edwin J. Gohr, SummihN. J., assgnors to StandardOil Development Company, a corporation of Dela- Ware , f Application December 28,1944, serialNo. 570,188

" t claims. (c1. 19e-5c)I This invention relates tothe lcracking vol. hydrocarbon oils and pertains more particularly to the cracking of oils in the` presence of a finelydivided cracking catalyst.

It has heretofore been the practice, to crack oils in the presence of a finely-divided cracking catalyst which is continuously circulated through a cracking zone and a regenerating zone and Min which the catalyst is maintained in a fluid state throughout its circulation between the cracking and regenerating zones by maintaininga small amount of iluidizing gas in admixture with said catalyst. It has previously been known that the presence of a small amount of such aerating gas causes the finely-divided catalyst to behave in many respects as a liquid, such as being capable of generating a'hydrostatic pressure. When operating according to previous practices, the pressure lost during circulation of the catalyst powder is restored by providing one or more standpipes in the circulating circuit. For example, one standpipe may be positioned in the transfer 2 operating a cracking eiciently utilizing the cracking equipment.`

Another main object of the invention is to utilize more effectively the heat liberated during the burning of combustible deposits from the catalyst during the regenerative treatment.

Other more detailed objects of the invention Awill be apparent from the descriptionhereinline for passing the catalyst from the cracking zone to the regenerating zone and another standpipe may be positioned in the transfer line leading from the regenerating zone back to the cracking zone. This type of process is generally known as the fluid cracking process.

, When operating the fluid catalyst process, and also other types of catalytic processes, it has been the practice heretofore to regulate the cracking conditions to convert a relatively uniform and predetermined amount of the charging oil into gasoline, irrespective of thecoke-forming characteristics of thecharging oil. This means that there is a variation in the amount of coke formed during the cracking Aoperation from a given amount of feed, depending upon the coking characteristics of the charging oil. Because of the variation in the amount of coke produced, according to prior practices it was necessary to design the regeneration chamber of suflicient capacity to burn the maximum amount of l coke which would be produced from the various types of charging oils vpassed to the equipment. In view of this, the regenerating equipment was opi erated at design capacity only in cases where the charging stock produced a relatively high percentage of coke. In other cases, such as when employing a relatively clean condensate stock which produced relativelylow amounts of coke,

the'regenerating equipment was not operated at l maximum capacity or eiliciency. i

One of the important objects of the present inventionis to provide an improved method of after in which reference will be made to the accompanying drawing which is a partly diagrammatic and partly schematicillustration of an apparatus capable of carrying the invention into effect.

In accordance with the oil to be cracked is passed upwardly through a vertical, reaction chamber into which'a stream of finely-divided powder is continuously introduced and the velocity of `the vapors rising through the chamber is controlled by the rate of feed of the charging oil to maintain a relatively dense, turbulent layer or phase of catalyst in the bottom portion of the cracking chamber.'

Under properly regulated conditions, this rela.-

tively dense layer will ,be superimposedby a relatively dilute phase containing oil vapors and a small amount of entrained catalyst. The levely of the dense, turbulent phase of catalyst in the cracking chamber is independently controlled by separately withdrawing a stream from the dense phase at a controlled rate.

Further in accordance with the present invention, the level of the dense, turbulent phase within the cracking chamber is regulated to convert a substantially uniform amount of the charging oil into coke or combustible deposits, irrespective of the coke-forming characteristics of the charging oil.

According to a. more-specific phase of the inven-l tion, the amount of c'oke formed is controlled so that the heat liberated during the burningthereof issulicient to supply the major portion of the heat requirements for the cracking process. This involves supplying the heat required to preheat the oil from incipient cracking temperature or below up to the nal cracking temperature and to supply the necessary heat for the endothermic reaction. When operating according to the present invention, the amount of charging stock converted into gasoline will vary with the coke-forming characteristics of the charge. Expressed in another way, instead of carrying out the cracking process to convert a uniform amount of charging oil into gasoline, according to present practices,

the cracking conditions are controlled to convert a uniform and predetermined amount of the oil present invention, the

into coke, the amountl of coke formed being sufclent to supply the necessary fuel for the cracking'process. This is accomplished according to a specic phase of the invention by regulating the level of the dense, turbulent phase of catalyst within the cracking zone.

Having set forth the general naturel and ob-v jects, the invention will be best understood by' the more detailed description hereinafter and reference will now be made to the accompanying drawing. v,

Referring tothe drawing, the reference character I designates a charge line for introducing the oil to be processed .into the system. This oil may comprise any higher boiling hydrocarbon oil fraction which is desired to be converted into gasoline or motor fuel constituents, including gas oils and crude residuums'. The oil prior to being introduced into the system through line I0 may above the desired cracking temperature and the amount introduced is sulcient to preheat the oil from the initial preheat temperature to the final desired cracking temperature and also to supply the necessary heat for the cracking reaction. The amount of catalyst so introduced will normally range between and 50 parts of catalyst per part of oil by weight. The finely-divided catalyst may consist of any of the cracking catalysts, such as activated clays andlsynthetic gels of silica-alumina, silica-magnesia, boron oxidealumina, silica-zirconia, and the like.

'I'he suspension of oil and catalyst formed in the line I0 is transferred into the bottom of a reaction chamber I3. The bottom of the reaction chamber I3 may be in the form of an inverted cone superimposed by a grid, I4 forming a distributing zone for distributing the oil vapors and catalyst into the main body of the cracking chamber. The size of the cracking chamber is designed to permit the velocity of the oil vapors to be reduced to a point which will cause the finely-divided powder to separate into a relatively dense phase in the bottom section of the reaction chamber, as illustrated. This layer of catalyst will be maintained in a highly turbulent condition by the oil vapors rising therethrough and a substantially uniform temperature may therefore be maintained throughout the body of catalytic material therein. l,

The oil vapors pass upwardly through the layer of catalytic material maintained in the cracking chamber and are removed overhead into a cyclone separator I5 whe'reinentrained catalyst is separated from the gaseous reaction products. The superiicial velocity of -the oil vapors rising through the reaction chamber may be of the order of from 0.5 to 5 feet per second, depending upon the size and density ofthe catalyst particles.

The reaction vapors are removed from cyclone separator I 5 through line I6 and the catalyst separated in the cyclone is returned to the cracking chamber through conduit I'I. The cracked vapors may be passed to a conventional fractionating column I8 in which .the vapors are subjected toI fractional condensation to separate the cracked products into a plurality of fractions. The initial fraction formed in the bottom portion of the i fractionating tower .I8 will normally contain a relatively small amount of catalytic material. The initial condensate. containing the powdered material is withdrawn from the bottom of the fractionating tower I8 through line I9 and may berejected from the system or it may be recycled to the reaction chamber for further cracking, if desired.` Condensate formed in the upper section of the fractlonating tower may be separately collected in one or more' trap-out trays, such as trap-out tray 2l, and separately withdrawn as a side stream through line 22.

Vapors remainingI uncondensed in the fractionating tower I8 are removed overhead through line 23 which leads to a condenser 24 in which the motor fuel constituents formed during the cracking process may be condensed. The prodl ucts th'en continue from the condenser 24 into a receiver 25 in which the liquid distillate separates from uncondensed vapors and gases. The vapors and gases are removed from the receiver. 25 through line 26 and may be passed to suitable recovery equipment which, for purposes of simplicity, has not been illustrated in the drawing.

.The raw distillate separated in the receiver 25 is withdrawn through line 21 and may be subjected to any further finishing treatment required for the production of the nal market product.

Referring again to the reaction chamber I3, a separate conduit 23 extends upwardly through the bottom of the reaction chamber into the main body of the chamber and preferably terminates at an intermediate point therein. The conduit 28 serves for separately withdrawing a stream of catalytic material containing absorbed reaction products from the reaction chamber. This stream discharges through a control valve 29 into a stripping zone 3-I in which the powder is subjected t o thorough stripping by an inert gas such ascombustion gas or steam to remove the volatile hydrocarbon products therefrom. The gas used for stripping is introduced into the bottom of the stripping zone 3l through line 32 and the volatile hydrocarbons together with the stripping gas are removed overhead through line 33 and may be introduced into the reaction chamber I3 above the level of catalyst therein and become intermingled with the main v apor product the vertical standpipe 35 in a fluid state capable of behaving as a liquid and thereby generating a hydrostatic pressure at the base of the standpipe. The powder discharges from the base of the standpipe 35 through a, control valve 38 at a controlled rate into a stream of air passing through line 39. The suspension of air and catalyst passes from line 39 into the bottom of a regenerator 4I below a grid plate 42. The regeneration chamber 4I is constructed similarly to the cracking chamber I3 and the diameter of the chamber is preferably such that the velocity of the air rising through the regenerator is reduced to a point which permits the powder to separate into a relatively dense layer, as previously described in canectiei;V with the regenen chamber` I3.,

'I'he catalyst is .subjected to regeneration withy Y' in the regenerating chamber 4If or.b urning conibustible deposits formed yon the catalystduring the cracking operation.` 'I'he ,spent combustion gases are removed overheadfrom the regenerator 4I through -a cyclone, whichy eifects ,further removal of catalyst powder fromI thespent combustion 7 gases. The catalyst separated in the cyclone 46 discharges back intothe regenerator through conduit, 43 andthe spent combustionA V gases are removedC overhead through line 44.

These combustion gases may be `passed tov addi-1 tional recovery equipmentsuch as Cottrell sepa rators, filter bags, andthe like forfurltheriseparation of the-catalyst.fromtheregeneration gas.,h As villustrated, theconduit II which discharges1 l the catalystinto themain feed ,stream passing through linel I'Ilhas `an extensionv 45 projecting throughthe` grid plate 42 and upwardly intothe This l amount of uidizing `gas Amay be` introducedlat` one orfmore spaced `points inlthe conduit yII to maintain the powder in a` fluid state and the con'- duit I I may function as conduit 35 for generating additional pressure to restore pressure lostdur4 ing passage through the regeneratingequipment. I

In accordance with the present invention, the amount' ofcokeformed from a'given amount of feed during the cracking process is maintained substantially uniform irrespective of the cokeforming characteristics `of the charge by varying the depth of the catalyst layer within the rel action chamber I3. The depth of the catalyst layer in the reaction chamber may be regulated by controlling the rate of withdrawal of the catalyst through control valves 29 and 38. The extent of crackingI in the cracking chamber I3 will depend upon the depth of the catalyst layer through which the oil vapors pass, .and when it is desired to reduce the amount of cracking which is taking place the level in the reactor is maintainedrelatively low, whereas when it is desired to increase the degree of cracking a greater depth `of catalyst is maintained within the reaction chamber. The minimum level maintained in the reaction chamber I3 will be fixed by the heightof the conduit 28 projecting into the reaction chamber, and the maximum level will depend upon the height of the reaction chamber.

It will tl'erefore be evident that the amount of catalyst maintained in the reaction chamber through which the oil vapors pass may be controlled over a relatively wide range and thus provides an excellent means of regulating the amount of coke formed during the cracking operation. The amount of coke formed from a given amount of feed is preferably sufficient to supply the major portion of the heat requirements for the cracking process, as previously set forth. This may range from 2% to 9% coke, depending upon the preheat temperature of the oil -and the cracking temperature desired. When operating at temperatures of about 950 F. in the cracking chamber and 1100 F, in the regenerator, the amount of coke formed should be about 6% when an oil preheat temperature of 400 F. to 500 F. is employed.

This application forms a continuation-impart of our earlier application Serial No. 363,867, led November 1'-, 1940.

` Having setl forththe igeneral nature Har jects of the invention, itV will be u ent is: 4

1. I n a pro'cessfforl cracking hydrocarbon oils,"

wherein the oilis cracked in the presence'of a cracking'zone and vwhereinoils ,Ofd'iifer'ent coking characteristics are passed through said' cracking rstoodi thatr it embraces such` other `variations and modifica" i tions as come within the spirit and'scope thereon j What is desired to be protectedby LettersPatf catalyst which continuously circulates through a zone at different times, the improvement which' comprises controlling the amountlof cataly'stuiri l said cracking zone ,to convert a substantiallyuniform and predetermined amuntofJtheoilinto, coke irrespective ofthecokefformingdcharacf teristics of said oil.A f 2. In a process for cracking hydrocarbon oils ,wherein the oil is` crackedin the presence of a e catalyst which continuously circulates throughv a cracking zone and thereafter through ia regenerating zone in which coke deposits formed o n the a `ca talyst,during.the cracking 'operation errores,r `moved by. burning and wherein oilsof different" coke-forming characteristics` areopassed through 1 said cracking` zone, at differentl times, the improvement which` comprises controlling the, amount of catalyst in said cracking zone to convert a substantially` uniform and predetermined amount of the oil into coke` irrespective of the coke-forming characteristics of said oil, ,the amountv of coke formed being` sufficient when4 burned in said regenerating zone to supply the` major portion ofthe heat requirements for the f cracking processburning thecoke formed` during the cracking process in said regenerating zone to 'heat the catalyst to a temperature materially above `the temperature 4existing in the cracking zone and thereafterreturning the heated catalyst directly from the regenerating zone to the cracking zone. f

3. A process for cracking hydrOCarbonoiIs which comprises passing the oils of different cokeforming characteristics in vapor form at different r times /upwardly through arr enlarged vertical cracking zone containing nely-divided cracking` catalyst, regulating the velocity of the vapors rising through said cracking zone to maintain a ,relatively dense, turbulent layer of catalyst in the bottom portion of the cracking zone, withdrawing vaporous cracked products from the upper end of said zone, continuously introducing a stream of hot, nely-divided catalyst into said cracking Zone, 'withdrawing a stream of finelydivided catalyst from the lower portion of-said cracking zone below the level of said dense, turbulent layer of catalyst and varying the amount of catalyst contained in said zone to convert a uniform amount of said oils into coke irrespective of the coke-forming characteristics of said oils during the cracking process.

4. A process for cracking hydrocarbon oils of different coke-forming characteristics. which comprises preheating the oils to a temperature below active cracking temperature, passing the zone below thelevel of said layer, passing the catalyst so withdrawn '.to a' regenerating zone, burning coke deposits from said catalyst within said regenerating zone to thereby heat said catalyst, returning the heated catalyst to the crackv ing zone and varying .the amount of catalyst within vsaid cracking zone to convert a uniform and predetermined amount of oils into said coke 'incipient cracking temperature, passing the heated oils in vapor format diierent times upposits formed on the catalyst during the cracking operation are burned with the liberation of heat and wherein the loss in pressure on the catalyst during circulation is restored bypassing the catalyst downwardly `through a vertical standpipe capable of generating a hydrostatic pressure; the improvement which comprises passing vthe oils in vapor form at diierent times upwardly through a cracking zone containing said catalyst at 'a velocity controlled to f orm a relativelydense layer ot catalyst in the bottom section of the cracking zone, removing vaporous reaction products from the upper end of the cracking zone. separately withdrawing nely-divided catalyst containing coke deposits from the lower portion of the cracking zone below .the level of said catalyst layer, passing the catalyst so withdrawn to a l regenerating zone, passing an oxidizing gas upwardly through an enlarged vertical cracking zone I containing n'ely-divided cracking catalyst, regu- 'lating the velocity of the vapors rising through said cracking zone to maintain a relatively dense, turbulent layerot said catalyst in the bottom portion of said zone, withdrawing vaporous cracked products from the upper end of said zone, separately withdrawing a stream of finelydivided catalyst containing coke deposits from the lower portion of the cracking zone, passing the catalyst so withdrawn to a regenerating zone, burning coke deposits fromsaid catalyst in the regenerating zone to thereby heat said catalyst, returning the heated catalyst to the cracking zone and regulating the level of the layer within said cracking zone to convert a uniform and predetermined amount of said oils into coke irrespective of the coke-forming characteristics thereof, the amount of said coke being suicient when burned in said regenerating' zone to supply the remaining heat requirements for the cracking process.

7. In a fluid catalyst cracking process for cracking oils of diierent coke-forming characteristics wherein iinely-divided cracking catalyst maintained in a fluid state is continuously circulated through a cracking zone and thereafter through a regenerating zone in which coke dewardly through said regenerating zone at a ve'- locity controlled to maintain a relatively dense layer'oi.' catalyst in said regenerating zone, removing spent regenerating gas from the upper portion of said regenerating zone, heating said catalyst within said regenerating zone, withdrawing catalyst from the lower portion of said Y I regenerating zone beneath the layer of said catalyst therein, returning the regenerated catalyst while in said heatedcondition to said cracking zone and varying the level of the catalyst within said cracking zone to convert a substantially uniform and predetermined amount of saidoils into coke irrespective of the coke-forming characteristics thereof.

CHARLES E. HEmnNGER.

EDWIN J. GOHR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 118,399 Australia Apr. 12, 1944 

